This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 2001-213494 filed in Japan on Jul. 13, 2001, the entirety of which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to an oil tank system for an engine, and more particularly to an oil tank system for a dry sump type engine in which an oil tank for storing engine oil is provided independently from the engine. An exemplary oil tank system is adapted specifically for an engine mounted on a small watercraft.
2. Description of the Background Art
In recent years, even for small watercraft (particularly, personal watercraft), four-cycle engines have been mounted on these craft in order to reduce environmental pollution due to exhaust gas and for the reduction of noise.
Since personal watercraft are configured such that an engine is substantially enclosed in a narrow space formed by a hull and a deck, the engine is required to be relatively compact. However, since a four-cycle engine has a valve system and further has a large cylinder head, the size of the four-cycle engine generally tends to be large.
Since four-cycle engine require forced lubrication of engine oil, the engine oil is liable to be entrained in crankcase gases circulating in a crankcase. In order to subject the crankcase gas to gas-liquid separation and introduce the gas from which engine oil has been separated again into a combustion chamber, there have been proposed various breather systems for accomplishing the gas-liquid separation.
For example, in conventional four-cycle engines, a breather chamber is formed only in a cylinder head cover (see Japanese Patent Laid-open No. Hei 10-252440).
However, since a breather chamber is formed only in a cylinder head cover in conventional four-cycle engines, the present inventors have determined that the entire size, particularly the overall height, of the engine becomes large. Accordingly, the task of mounting a four-cycle engine in a small watercraft body has become exceedingly difficult.
The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.
An object of the present invention is to provide an oil tank system for an engine, which is capable of reducing the size, e.g., the height, of the engine.
An object of the present invention is to provide an oil tank system that solves the aforementioned problems associated with the background art and otherwise not realized by the background art.
One or more of these and other objects are accomplished by an oil tank system for a dry sump engine, the oil tank system comprising an oil tank for storing engine oil provided independently from the engine; and a breather chamber being provided within the oil tank, the breather chamber being in fluid communication with the engine.
One or more of these and other objects are further accomplished by an oil tank system for a dry sump engine of a personal watercraft, the dry sump engine driving a jet pump drive of the personal watercraft, the oil tank system comprising an oil tank for storing engine oil provided independently from the engine; a breather chamber being provided within the oil tank, the breather chamber being in fluid communication with the engine; a water-cooled oil cooler; and an oil cooler accommodating portion formed integrally with the oil tank, wherein cooling water from a cooling water takeoff portion in the jet pump is first supplied to the water-cooled type oil cooler accommodating portion.
According to an alternative aspect of the present invention, the oil tank may include divided cases joined to each other, and the breather chamber being formed by joining the divided cases to each other. Further, a breathing gas inlet for supplying breathing gas to the breather chamber may be provided in an upper portion of the oil tank. A breathing gas outlet for discharging the breathing gas from the breather chamber is provided at a position lower than that of the breathing gas inlet and an oil return passage for returning oil having been separated in the breather chamber is provided in the oil tank.
Alternatively, or in combination therewith, the divided cases of the oil tank are joined to each other via a gasket; the breather chamber is partially partitioned into a first breather chamber and a second breather chamber by the gasket; and the breathing gas inlet is provided in the first breather chamber and the breathing gas outlet is provided in the second breather chamber. Alternatively, or in combination therewith, the oil tank forms a cover portion of an AC generator disposed at an end of a crankshaft of the engine.
A pulser for extracting a signal may be provided on an outer periphery of the AC generator in such a manner as to overlap the oil tank in a direction along the crankshaft. A water-cooled type oil cooler accommodating portion for an oil cooler may be formed integrally with the oil tank.
Alternatively, and/or in combination therewith, an oil filter is provided in the oil tank and the oil cooler is interposed in an oil passage extending from the oil filter to a main gallery of the engine. If the engine is an engine mounted on a small watercraft for driving a jet pump, cooling water from a cooling water takeoff portion in the jet pump is first supplied to the water-cooled type oil cooler accommodating portion. Further, the breather chamber may form an oil sump during a turn-over condition of the watercraft and/or oil system. The return passage may form a breathing passage during the aforementioned turn-over condition of the watercraft. The sump portion for a counter flow of oil in the return passage during the turn-over condition of the watercraft may be provided in an upper portion (lower portion, during the turn-over condition of the watercraft) of the second breather chamber.
The breather chamber of a dry sump type engine in which the oil tank for storing engine oil is provided independently from the engine is defined in the oil tank and the breather chamber is in communication with the engine. Accordingly, it is possible to eliminate the need for of provision of a breather chamber in a head cover or the like of the engine. Therefore, it is possible to significantly reduce the volume of the breather chamber.
It also possible to reduce the entire size, particularly, the overall height of the engine and to more easily accommodate a four-cycle engine in a small watercraft body. As a result, it is possible to provide a smaller watercraft that still capitalizes on the reduced environmental pollution and noise benefits of four-cycle engines.
If the oil tank is composed of divided cases joined to each other, and the breather chamber is formed by joining the divided cases to each other, it is possible to freely set the volume, shape, and the like of the breather chamber. If the breathing gas inlet of the breather chamber is provided in the upper portion of the oil tank and the breathing gas outlet of the breather chamber is provided at a position lower than that of the breathing gas inlet and the return passage is provided in the oil tank, it is thus possible to ensure adequate height is provided for gas-liquid separation in the breather chamber, and to simplify the return of separated oil.
The divided cases are joined to each other via the gasket, and the breather chamber is partitioned into the first breather chamber and the second breather chamber via the gasket. The breathing gas inlet may be provided in the first breather chamber and the breathing gas outlet may be provided in the second breather chamber. It is thus possible to perform gas-liquid separation more reliably.
If the oil tank forms the cover portion of the AC generator disposed at an end of the crankshaft of the engine, it is possible to reduce the number of required parts and to obtain a desirable noise absorption effect, e.g, due to the surrounding oil as compared with a single cover liable to induce radiation noise occurring from the engine. Accordingly, it is possible to reduce the degree of noise occurring from the engine.
The pulser for taking out a signal is provided on the outer periphery of the AC generator in such a manner as to overlap the oil tank in a direction along the crank shaft. Accordingly, the axial length required for the pulser does not need to be elongated. As a result, it is possible to make the engine more compact.
The water-cooled type oil cooler accommodating portion may be formed integrally with the oil tank. Therefore, it is possible to simplify an oil piping structure and a cooling water piping structure. If the oil filter is provided in the oil tank and the oil cooler is interposed in the oil passage extending from the oil filter to the main gallery of the engine, it is possible to supply the coolest oil from the system to the main gallery of the engine.
If the engine is an engine mounted on a small watercraft for driving a jet pump and cooling water from the cooling water takeoff portion of the jet pump is first supplied to the water-cooled type oil cooler accommodating portion, it is possible to efficiently cool not only oil passing through the oil cooler, but also oil stored within the oil tank. Alternatively, or in combination therewith, the breather chamber may form the oil sump portion for accumulating oil the turn-over condition of the watercraft. Therefore, it is possible to prevent the outflow of oil during this condition.
If the return passage forms the breathing passage during the turn-over condition of the watercraft, it is possible to prevent the outflow of oil with more certainty. If the sump portion for oil which counter flows in the return passage during the turn-over condition of the watercraft is provided in the upper portion (lower portion, during the turn-over condition) of the second breather chamber, it is possible to prevent the outflow of oil with more certainty.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.